Method and apparatus for performing targeted interference suppression

• US 6,131,013 A
• Filed: 01/30/1998
• Issued: 10/10/2000
• Est. Priority Date: 01/30/1998
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Kleider, John Eric, Chuprun, Jeffrey Scott, Bergstrom, Chad Scott
• Primary Examiner(s): Trost, William G.
• Assistant Examiner(s): GELIN, JEAN ALLAND
• Application Number:
  US09/016,030
• Time in Patent Office: 984 Days
• Field of Search: 455/63, 455/67.1, 455/67.3, 455/296, 455/226.1, 455/226.2, 455/226.3, 455/501, 455/504, 455/506, 375/285, 375/346, 375/347, 375/348, 375/350, 379/392, 379/406, 379/410, 379/416, 379/3, 381/317, 381/318, 381/93, 381/71.1
• US Class Current: 455/63.1
• CPC Class Codes: H04B 1/123 using adaptive balancing or compensation means adaptive filter circuits and algorithms H03H
• CPC Class Codes: H04L 1/0001 Systems modifying transmission characteristics according to link quality, e.g. power backoff adaptive data allocation for multicarrier modulation H04L5/0044; controlling transmission power for radio systems H04W52/04
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/20 using signal quality detector
• CPC Class Codes: H04L 27/0012 arrangements for identifying the type of modulation

Abstract

The invention relates to a communication system (300) having a receiver (304) that is capable of performing targeted interference suppression. An interference classifier (314) within the receiver (304) analyzes a signal received from a channel (306) and identifies and classifies interference components within the signal. An interference suppressor (316) then suppresses the interference components in the signal based on interference type. In one embodiment, the interference suppressor (316) includes a plurality of interference suppression modules that are each optimal for suppressing certain interference types. The interference suppressor (316) selects one of the interference suppression modules based on the type of interference present in the received signal. In another embodiment, a hybrid interference mitigation system (10) is provided by combining targeted interference suppression, frequency hopping adaptation, and processing gain adaptation.

Claims

1. A receiver unit for use in a communications system that is operative in a predetermined frequency band, comprising:

a signal receptor for receiving a signal from a communications channel;

an interference classifier for classifying an interference component within said signal, wherein said interference classifier classifies said interference component according to a plurality of interference types, and said interference classifier outputting a signal indicative of classification of each of said interference types; and

an interference suppressor for suppressing said interference component by selecting one of a plurality of suppression methods best suited to suppress said signal based on the indication signal of classification of said interference type.

2. A receiver unit, as claimed in claim 1, wherein:

said interference suppressor includes means for selecting from a plurality of interference suppression methods best suited to suppress said interference type, based on interference type.

3. A receiver unit as claimed in claim 1, wherein said interference suppressor includes:

a plurality of interference suppression modules for use in suppressing interference in said signal; and

means for selecting at least one of said interference suppression modules best suited to suppress said interference type, based on interference type.

4. A receiver unit, as claimed in claim 3, wherein:

said interference suppression modules are each optimized for use with predetermined interference types.

5. A receiver unit, as claimed in claim 3, wherein:

said means for selecting includes means for selecting multiple interference modules based on multiple interference components in said signal, wherein said interference suppressor cascades said multiple interference modules to process said signal.

6. A receiver unit, as claimed in claim 1, wherein:

said interference classifier includes at least one of the following;

a multi-layer perceptron classifier and a decision tree classifier.

7. A receiver unit, as claimed in claim 1, wherein:

said interference classifier includes means for extracting parameters relating to said interference component from said signal.

8. A receiver unit, as claimed in claim 7, wherein:

said means for extracting parameters includes a means for determining at least one feature parameter transformation for said interference component.

9. A receiver unit, as claimed in claim 8, wherein:

said means for determining at least one feature parameter transformation includes means for receiving input in-phase signal samples x(i) and quadrature signal samples y(i) and for processing the samples according to the following transformation equations;

space="preserve" listing-type="equation">px(j)=y(i+τ

)[y(i)-x(i)]+x(i+τ

)[x(i)+y(i)]

space="preserve" listing-type="equation">py(j)=x(i+τ

)[x(i)-y(i)]+y(i+τ

)[y(i)+x(i)]

where px(j) and py(j) are the in-phase and quadrature transformations, respectively;

τ

=delay, in samples;

i=1 to N; and

j=1 to N-τ

.

10. A receiver unit, as claimed in claim 8, wherein:

said means for determining at least one feature parameter transformation includes means for generating a histogram.

11. A receiver unit, as claimed in claim 8, wherein:

said means for determining at least one feature parameter transformation includes means for performing a polar to Cartesian transformation.

12. A receiver unit, as claimed in claim 8, wherein:

said means for determining at least one feature parameter transformation includes means for performing a histogram magnitude projection.

13. A receiver unit, as claimed in claim 8, wherein:

said means for determining at least one feature parameter transformation includes means for performing a histogram phase/frequency projection.

14. A receiver unit, as claimed in claim 7, wherein:

said interference classifier includes a memory means for storing parameters for known interference types, said stored parameters being for comparison with parameters extracted from said signal.

15. A receiver unit, as claimed in claim 1, wherein:

said interference classifier includes a co-processor for performing complex arithmetic operations.

16. A receiver unit, as claimed in claim 1, further comprising:

a performance estimator for determining at least one performance metric relating to the performance of said communications system and feedback means for delivering said at least one performance metric to said interference suppressor for use in fine tuning the interference suppressor.

17. A receiver unit, as claimed in claim 1, wherein:

said communications system is a spread spectrum personal communications system (PCS) that overlays a narrowband/partialband communications system.

18. A receiver unit, as claimed in claim 1, wherein:

said communications system is a spread spectrum paging system that overlays a narrowband/partialband communications system.

19. A receiver unit, as claimed in claim 1, wherein:

said communications system is a wireless LAN system that overlays a narrowband/partialband communications system.

20. A receiver unit, as claimed in claim 1, wherein:

said receiver unit is part of a handheld transceiver capable of duplex operation.

21. A receiver unit, as claimed in claim 1, wherein:

said interference classifier includes means for improving the signal to noise ratio (SNR) of said signal before classification is performed.

22. A receiver unit, as claimed in claim 21, wherein:

said means for improving SNR includes

preclassification filtering means for use in separating an interference component from said signal.

23. A receiver unit, as claimed in claim 21, wherein:

said means for improving SNR includes a phase domain filter.

24. A receiver unit, as claimed in claim 23, wherein:

said phase domain filter is for use in separating a plurality of interference components.

25. A receiver unit, as claimed in claim 23, wherein:

said phase domain filter comprises a moving average.

26. A method for reducing interference components in a received signal in a communications system, comprising the steps of:

receiving a signal from a channel;

classifying at least one interference component in said signal according to interference type; and

performing interference suppression on said signal to reduce the level of said interference component within said signal, said performing step including selecting an interference suppression method from a plurality of interference suppression methods based on interference type.

27. The method, as claimed in claim 26, wherein:

said classifying step includes extracting parameters from said signal relating to said interference component.

28. The method, as claimed in claim 26, wherein:

said classifying step includes seperating said interference components from a plurality of interference components.

29. The method, as claimed in claim 26, wherein:

said plurality of interference suppression methods includes an adaptive excision method including the following steps;

obtaining a frequency domain representation of said signal;

determining a frequency location of said interference component with respect to said frequency domain representation; and

removing a portion of said frequency domain representation of said signal based on said frequency location of said interference component.

30. The method, as claimed in claim 29, wherein:

said removing step includes applying a band-reject filter to said frequency domain representation.

31. The method, as claimed in claim 26, wherein:

said plurality of interference suppression methods includes an inverse weight method including the following steps;

obtaining a frequency domain representation of said signal;

determining portions of said frequency domain representation that exceed a limit value; and

reducing said portions in magnitude using an inverse weighting function.

32. The method, as claimed in claim 31, wherein:

said inverse weighting function is inversely proportional to the difference between a magnitude of said portions and said predetermined limit value.

33. The method, as claimed in claim 32, further comprising the step of:

adaptively adjusting said limit value based on a predetermined criterion.

34. The method, as claimed in claim 33, wherein:

said predetermined criterion includes a signal strength estimate for said interference component.

35. The method, as claimed in claim 33, wherein:

said predetermined criterion includes a standard deviation estimate for said interference component.

36. The method, as claimed in claim 33, wherein:

said predetermined criterion includes a bandwidth estimate for said interference component.

37. The method, as claimed in claim 26, wherein:

said plurality of interference suppression methods includes an inverse whitening method including the following steps;

obtaining a frequency domain representation of said signal;

determining a spectral envelope of said interference component using said frequency domain representation;

generating an inverse envelope function using said spectral envelope; and

applying said inverse envelope function to said frequency domain representation of said signal to reduce said interference component in said signal.

38. The method, as claimed in claim 26, wherein:

said plurality of interference suppression methods includes an inverse whitening method including the following steps;

determining a spectral envelope using time domain samples of said signal;

generating an inverse envelope function using said spectral envelope; and

applying said inverse envelope function to said time domain samples.

39. A communications system having hybrid interference mitigation, said system comprising:

means for receiving a signal from a channel;

means for classifying at least one interference component within said signal according to interference type , and said interference classifier outputting a signal indicative of classification of each of said interference types;

means for suppressing said at least one interference component by selecting one of a plurality of suppression methods best suited to suppress said signal based on the indication signal of classification of said interference type; and

adaptation means including at least one of the following;

means for performing frequency hopping adaptation by updating a frequency hopping sequence in response to said means for classifying; and

means for performing processing gain adaptation by updating the processing gain of a transmit signal in response to said means for classifying.

40. The communications system, as claimed in claim 39, wherein:

said adaptation means includes both means for performing frequency hopping adaptation and means for performing processing gain adaptation.

41. The communications system, as claimed in claim 39, wherein:

said adaptation means is enabled when an output signal of said means for suppressing fails to achieve a predetermined performance goal.

42. The communications system, as claimed in claim 41, wherein:

said predetermined performance goal includes a bit error rate (BER) being less than a predetermined value.